1. Field of the Invention
This invention relates to a printed circuit board, and more particularly to a printed circuit board on which leadless circuit-parts are mounted.
2. Description of the Prior Art
Hitherto, such a cylindrical leadless circuit-part 4 as shown in FIG. 1 and FIG. 2 is known. Caps 2 and 3 as electrodes are attached to both ends of a cylindrical body 1 in the cylindrical leadless circuit-part 4. In the mounting process, the cylindrical leadless circuit-part 4 is provisionally attached to a printed circuit board 5 with adhesive. FIG. 1 and FIG. 2 show the condition that the cylindrical circuit-part 4 is provisionally attached to a predetermined position on the printed circuit board 5 with adhesive 6. Patterns 7 and 8 of copper foil and a solder-resisting layer 9 are formed on the circuit board 5. The circuit-part 4 is provisionally attached to the circuit board 5 in the manner that the caps 2 and 3 of the circuit-part 4 contact with electrode portions 7a and 8a of the patterns 7 and 8. The printed circuit board 5 with the circuit-part 4 is dipped into a solder bath. Thus, the caps 2 and 3 of the circuit-part 4 are soldered to the electrode portions 7a and 8a of the patterns 7 and 8. The circuit-part 4 is firmly mounted on the circuit board 5 at a mechanically and electrically sufficient combining strength.
In the provisional attaching process, the predetermined position between the electrode portions 7a and 8a on which the circuit-part 4 should be mounted in the circuit board 5, is coated with adhesive 6 by a screen-printing method or a dispenser injection method, and then the circuit-part 4 is put on the predetermined position to be provisionally attached, as shown in FIG. 1 and FIG. 2. In this case, it is important that the predetermined position is accurately coated with adhesive 6 in a predetermined range. However, in the conventional printed circuit board, it cannot be easily discriminated whether the predetermined position has been accurately coated with adhesive 6 or not. Particularly in a hybrid integrated circuit in which numerous circuit-parts of such a kind are mounted, it is very difficult to find defects such as coating deflections from exact positions and blots from numerous coated positions with the naked eyes. Such difficulty causes the lowering of the working efficiency and the decrease of the reliability of the produced printed circuit board.